Radio device including a receiver and method of adjusting one of the high-frequency amplifier stages of a receiver

ABSTRACT

A radio device includes a receiving part ( 45 ) formed by a high-frequency selective amplifier stage ( 50 ) including a frequency selective circuit ( 51 ) having a plurality of capacitive elements ( 68-78 ), any one or more which can be selectively connected into the selective circuit in dependence on a control magnitude stored in a storage element ( 90 ) in order to tune the selective circuit to a certain frequency. Under the control of a microprocessor ( 92 ) the stored control magnitude is set to that which gives the best level measured by a level detector ( 98 ) at the output of the amplifier stage. The microprocessor varies the control magnitude to produce a series of alternate connections into the selective circuit of each and every combination of one or more of the reactive elements, receives the measurement by the level detector of the level at the output of the amplifier stage or each control magnitude, and selects the control magnitude giving the best level.

BACKGROUND OF THE INVENTION

The present invention relates to a radio device comprising a receivingpart formed by at least:

a selective high-frequency amplifier stage including a selective circuitthat can be tuned to a certain tuning frequency.

The invention also relates to a method of adjusting one of thehigh-frequency amplifier stages included in such a device.

Such devices are well known and find many applications, notably in thefield of portable telephones. It is necessary for this type of device tohave a sensitive receiver that increases its range. The use of aselective amplifier improves the sensitivity.

A problem posed with such devices is the tuning of this selectiveamplifier. During manufacture, components are used whose values featurecertain dispersion. One is thus confronted with the fact that the tuningfrequency of the selective amplifiers varies from one specimen to theother at the end of the manufacture and also varies in dependence ontemperature. To compensate this, habitually an adjusting capacitor isprovided and its value is influenced so that the selective circuit iswell tuned to the frequency band in which it is to operate. Atemperature compensation is described in Japanese patent specificationno. 07022974 of 24.01.1995. This compensation acts on a variablecapacitance diode that also tunes the oscillation circuit, so that thetotal variation that can be applied to this diode is burdened with thiscompensation.

SUMMARY OF THE INVENTION

The present invention proposes a device of the type defined in theopening paragraph in which means are provided for facilitating thetuning of the selective stage without using notably the temperaturemeter and means for maintaining the voltage dynamic that can be appliedto the tuning voltage if the selective circuit requires a certaindynamic in the tuning of its selective circuit. Therefore, such a deviceis characterized in that it comprises:

a received level meter for measuring the received level of the signalstransmitted by a reference oscillator,

a variation element for causing the tunable band-pass circuit to vary asa function of a control magnitude,

a storage element for storing the control magnitude that gives the bestlevel obtained by the level meter.

One of the ideas of the invention is to insert into the selectivecircuit one or various reactive elements that enable to center thisselective circuit on the frequency range in which the device is supposedto operate.

These and other aspects of the invention are apparent from and will beelucidated, by way of non-limitative example, with reference to theembodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWING

In the drawings:

FIG. 1 shows a device in accordance with the invention,

FIG. 2 shows the detail of embodiment of the invention,

FIG. 3 is a flow chart intended to explain the functioning of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 is represented an electronic device in accordance with theinvention. Within the framework of the described example, this is awireless electronic device, for example, of the CTO type. It comprises amicrophone 5, an earphone 6, a display 8, a keyboard 9 and an antenna11. This device is connected to its base station (not shown in the FIG.)by utilizing a frequency channel. It is to be observed that theinvention may also be applied to the base station itself.

FIG. 2 shows the transmitting part 40, not in detail because it does notform part of the invention, and the receiving part 45. It is in thisreceiving part that the selective amplifier is located which is thehigh-frequency preamplifier. This amplifier is shown diagrammatically inthis Figure. by an actual amplifier 50, at the output of which aselective anti-resonant circuit 51 is provided. This anti-resonantcircuit is formed by a self-inductance coil 55 to the ends of which amain capacitor 65 is connected which sets in a first approximation thetuning frequency of this anti-resonant circuit. This capacitor may alsobe a varicap diode.

According to the invention, for making the tuning frequency of thisselective circuit vary, other capacitors 68, 69, 70 and 71 are provided.For this purpose, they can be connected in parallel with the maincapacitor 65 via a connection circuit formed by the switch circuit 78,79, 80 and 81 respectively. The open or closed position of these switchcircuits is determined by the contents of a counter 90. The contents ofthis counter 90 are incremented under the control of a microprocessor 92and this counter 90 is also reset to zero under the control of thismicroprocessor 92. Thus, the assembly formed by the capacitors 68, 69,70 and 71 and the switch circuits 78, 79, 80 and 81 forms an element forvarying the tuning frequency controlled by the contents of the counter90. This microprocessor also receives a signal coming from a leveldetector 98. This level detector 98 is connected to the output of amedium frequency filter 100. This filter shows a medium frequency signalobtained by a mixer 105, which performs the mixing of the signalssupplied by the selective amplifier 50 including the anti-resonantcircuit 51 and a local oscillator 110. For adjusting the capacitance tobe connected in parallel with the main capacitor 65, a referencetransmitter 150 is used. The various capacitors are connected in turn inparallel with the anti-resonant circuit 51, thereby forming a tunableband-pass filter circuit. The combination applied to this anti-resonantcircuit 51 that offers the best-received level is stored, for example,by freezing the contents of the counter 90.

FIG. 3 is a flow chart that explains the functioning of the invention.Box K0 indicates the input of the adjusting process of the value of thecapacitors to be inserted into the oscillating circuit 51. This processis implemented in principle by the microprocessor 92. Box K1 indicatesthe initialization of two variables: first the variable C which is thecontents of the counter 90, that is to say, the contents of this counter90 are set to zero, and a variable N intended to contain the value ofthe level measured by the detector 98. In box K3, the value of thedetected level is received. This level is due to the emission of thereference emitter 105 started previously. This level is then compared,as indicated in box K5, with the level entered in the variable N. If thelevel Nc that has just been supplied is higher than the already enteredvalue, the latter value of Nc is stored in the variable N. Furthermore,the value of the contents of the counter 90 is stored in a variable CM(box K8). After the operation carried out in box K8 and if the testindicated in box K9 is negative, a test is made with the contents C ofthe counter 90. There is tested whether these contents are equal to 15,box K10, which corresponds to a 4-position counter that counts, inbinary count, from 0000 to 1111. If the contents of 15 are not obtained,this counter is incremented by unity in box K12. If these contents areequal to 15, the value CM which is thus associated to the highestdetected level is set in box K14. Box K15 marks the end of the executionof the program after the operation of box K14. The values C68, C69, C70and C71 of the capacitors 68, 69, 70 and 71 respectively, are eachother's double values such as:

C68=1.CO

C69=2.CO

C70=4.CO

C71=8.CO

so that all the values from 0.CO to 15.CO are obtained when the contentsof the counter 90 vary from 0 to 15, CO being the basic unit for theseseveral capacitors.

As a variant it is possible that the contents of the counter 90 arestored for various frequencies processed by the reference oscillator150, so that adjustments can be made to the various carriers the devicecan receive.

Although capacitors are cited for regulating the oscillation circuit,also reactive elements realized by self-inductances can be used withoutleaving the scope of the invention.

What is claimed is:
 1. A radio device comprising a receiving part formedby at least: a frequency selective stage including at least oneamplification stage followed by an anti-resonant frequency selectivecircuit that can be tuned to a certain frequency band, a level detector,coupled to an output of the frequency selective stage, for measuring thelevel of an external reference signal, a variation element for causingthe frequency band to which the tunable frequency selective circuit istuned to vary as a function of a control magnitude, said variationelement comprising a plurality of reactive elements and a connectionnetwork for selectively connecting any one or more of the plurality ofreactive elements into the frequency selective circuit in response tothe control magnitude, a storage element for storing the controlmagnitude, and a processor arranged to set the stored control magnitudeto that which gives the best level obtained by the level detector.
 2. Adevice as claimed in claim 1, wherein the variation element furthercomprises a counter for alternately connecting each and everycombination of one or more, of the reactive elements into the frequencyselective circuit, and the control magnitude is the contents of thecounter.
 3. The radio device as claimed in claim 1, wherein theanti-resonant frequency selective circuit comprises an inductor inparallel with a capacitance, wherein the capacitance is formed by theparallel arrangement of a plurality of capacitors.
 4. A method ofadjusting at least one frequency selective stage of a receiver, whereinthe frequency selective stage includes at least one amplification stagefollowed by an anti-resonant frequency selective circuit comprising avariation element for causing the frequency band to which the tunablefrequency selective circuit is tuned to vary as a function of a controlmagnitude, said variation element comprising a plurality of reactiveelements and a connection network for selectively connecting any one ormore of the plurality of reactive elements into the frequency selectivecircuit, the method comprising the following acts steered by aprocessor: alternate connection via the connection network of each andevery combination of one or more of the reactive elements into theanti-resonant frequency selective circuit, measurement of the levelreceived from an externally received reference signal, and storage ofthe control magnitude associated with the combination giving the bestlevel.
 5. The method as claimed in claim 4, including the step ofproviding an anti-resonant frequency selective circuit that comprises aninductor in parallel with a capacitance, wherein the capacitance isformed by the parallel arrangement of a plurality of capacitors.